The London Outer Orbital Path — more usually the "London LOOP" — is a 150-mile (242 km) signed walk along public footpaths, and through parks, woods and fields around the edge of Outer London, England, described as "the M25 for walkers". The walk begins at Erith on the south bank of the River Thames and passes clockwise through Crayford, Petts Wood, Coulsdon, Banstead, Ewell, Kingston upon Thames, Uxbridge, Elstree, Cockfosters, Chingford, Chigwell, Grange Hill and Upminster Bridge before ending at Purfleet, almost directly across the Thames from its starting point. Between these settlements the route passes through green buffers and some of the highest points in Greater London.

Erith is an area in south-east London, England, 13.3 miles (21.4 km) east of Charing Cross. Before the creation of Greater London in 1965, it was in the historical county of Kent. Since 1965 it has formed part of the London Borough of Bexley. It lies north-east of Bexleyheath and north-west of Dartford, on the south bank of the River Thames.